The present invention relates generally to radio-frequency (RF) and microwave filters and more specifically for a dual RF filter having a small package size for integration within telecommunications devices.
RF and microwave filters are used in telecommunications devices to reject out-of-band signals, filter undesired harmonics and spurious components from signals prior to transmission and for performing various other functions within the telecommunications devices.
In particular, a Groupe Spxc3xa9cial Mobile. (GSM) filter is typically required in the output of the transmitter for GSM transceivers and a Digital Cellular System (DCS) filter is typically required in the output of the transmitter for DCS transceivers. Both are typically required for a dual-mode telecommunications transceiver. Similar filters are also needed in wireless local area network (LAN) and wireless personal area network (WPAN) devices, such as BLUETOOTH and 802.11 devices. The above-mentioned filters occupy a significant amount of circuit board area and package volume within a dual-mode transceiver.
Small size and light weight components are critical to reducing the size of telecommunications transceivers and the trend is toward progressively smaller devices. Therefore, it would be desirable to reduce the size of required filters within telecommunications transceivers and further desirable to provide such reduction in a dual-mode telecommunications receiver wherein both a GSM and a DCS filter are required.
The above objectives of reducing filter size and providing a GSM and DCS filter that required less package volume and circuit board area are provided in a low-profile dual filter module that integrates two RF filter in one low-profile package. The dual filter module includes a first and second filter section each formed by multiple dielectric layers with metal circuit patterns sandwiched in between. The construction provides isolation between two filters in the same small package.